Process for loosening the skins of fruits and vegetables



THfOAET/(AL 72-11,? a; M/XTURE 6? Oct. 27, 1959 R. M. MAGNUSON ETAL 2,910,393

PROCESS FOR LOOSENING THE SKINS OF FRUITS AND VEGETABLES Original Filed April 18, 1949 5 Sheets-Sheet l FIG. I. 23

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P57609765 5754M //v Mara/v5 (7074A) 0 0.2 0.3 a4 a a; 0.7 a5 0.9 m M A2 0/ j INVENTORS 475? 4005a 70 M/ATI/RE (1a; mvrik P5? m it MHZ/R41 641/ i gj g a ATTORNEY Oct. 27, 1959 MAGNUSON 2,910,393

PROCESS FOR LOOSENING THE SKINS OF FRUITS AND VEGETABLES Original Filed April 18 1949 5 Sheets-Sheet 2 IN VEN TORJ #07 /V. MAM/V0.70 TIMI 5K J SM! 7H ATTORNEY 0a. 27, 1959 MAGNUSON 2,910,393

PROCESS FOR LOOSENING THE SKINS OF FRUITS AND VEGETABLES Original Filed April 18, 1949 3 Sheets-Sheet 5 24 36 TIME fire-comm) 7'0 PEEL M G 9 m R N m m w R W W 0m APPfA/ff [MB 4 (1mm EQR 99 3 Ft 3.

50km; o w/ wazm #26563 TIME $5 United States Patent 7 PROCESS FOR LOOSENING THE SKINS 0F FRUITS AND VEGETABLES Roy M. Magnuson and Traver J. Smith, San Jose, Calif., assignors, by direct and mesne assignments, of one-half to California Packing Corporation, a corporation of New York, and one-half to Genevieve I. Magnuson, executrix of said Roy M. Magnuson, deceased Continuation 'of application Serial No. 88,194, April 18, 1949. This application November 30', 1953, Serial No. 394,919

7 Claims. (Cl. 146241) an advantageous manner without objectionable oxidiz-' ing, charting or the like to facilitate subsequent removal of the skin by manual or automatic methods.

' Previous high temperature peeling processes have employed the use of steam under pressure to loosen the skin on certain fruits and Vegetables and thereafter removed the peel. The use of the steam peeler is limited by the various properties of steam in that practical working pressure of saturated steam limits the temperature and vice versa. At atmospheric pressure, no great advantages are found over ordinary hot water loosening of the skins. At pressures above atmospheric there is re quired a steel chamber with complicated valve constructions for entrance and exit of the articles to be peeled and the temperature rise is definitely limited by commercially feasible pressure in equipment of this type.

The other, type of high temperature peeling now available is knOWn as flame peeling and while this provides very high temperatures in the neighborhood of 2700 degrees to 3000 degrees F. the equipment deteriorates rapidly at such temperatures so that frequent replacement is necessary. Also the product is charred in many cases and is always dehydrated to a certain extent. Thus, there is danger of carbon in the final product as well as obtaining a product that is too dry.

Another object of the invention is to provide apparatus and methods of the above character which permit the high temperature conditioning in a substantially oxygen free atmosphere.

Still another object of the invention is to provide apparatus and methods of the above character in which the conditioning operation can be adjusted easily to the article In accordance with the instant invention higher tern peratures are provided than can be successfully obtained with steam pressure Whileremaining below temperature which will char the fruit or vegetable. At the same time the treating atmosphere is controlled to be substantially oxygen free so that no noticeable oxidation of the flesh of the fruit will occur. These higher temperatures are obtained at atmospheric pressure so that the apparatus can be relatively simpleand inexpensive as compared with other apparatus, andspecifically this is obtained by providing a controlled combustion process and applying the combustion products as a treating atmosphere to the fruit or vegetable being peeled. Preferably, the treating atmosphere is also conditioned for more effective heat transfer by the presence of moisture in the form of superheated steam.

Accordingly, it is a general object of the invention to provide a new method and apparatus for high temperature conditioning of fruit and vegetable articles for peeling. 7

Another object of the invention is to provide a new method and apparatus for high temperature conditioning of tomatoes to allow removal of a thinner skin than is possible with known processes.

to be peeled.

Still another object of the invention is to provide methods and apparatus of the above character in which the articles being treated can be adjustably moved during travel through and conditioned in the heating zone to.

advantageously treat all surfaces of the articles.

Still another object of the invention is to provide apparatus and methods of the above character in which the treating atmosphere contains moisture preferably in the form of superheated steam for more effective heat transfer to the articles being treated.

The above and other objects of the invention will become apparent from the following description of a preferred embodiment thereof as illustrated in the accompanying drawings, in which:

Figure 1 isa side elevational view of apparatus embodying the invention.

Figure 2 is an enlarged longitudinal sectional view of the apparatus with certain parts shown in elevation and others indicated schematically.

Figure 3 is a graph illustrating the theoretical conditions of the heating atmosphere plotted in logarithmic fashion to expand the curve portion of greatest interest under the present process.

Figure 4 is a graph showing the effect of temperature and time on tomato skin loosening.

Figure 5 is a graph showing the etfect of water injection on high temperature tomato peeling.

Figure 6 illustrates the key to the indicia used in Figures 4 and 5.

' The process will be described with reference to the treatment of tomatoes although it will be obvious that the process will be applicable to other fruit and vegetable articles of the type commonly processed in heat conditioning or peeling operations.

1 In carrying out the process the article to be peeled is first subjected to the conventional washing and sorting operations so that clean defect-free articles are carried through the peeling process.

After the articles have been washed, sorted and treated in the desired manner in the preparation for the peeling loosening operation, the articles are carried or transferred immediately into a heat application zone in which the articles are desirably supported for movement or rotation so that the shifting about of the articles will expose all of the skin uniformly to the heating medium. Desirably, both the rate of travel through the heating zone and the rate of movement or rotation of the articlesv articles. This heating zone may be connected to or disposed at one side of a combustion chamber which is provided with means for the introduction of (l) a fuel to be burned, such as gas, (2) air to effect the combustion of the fuel, and (3) moisture, with all of the elements individually controlled with respect to each other to obtain the desired result. The amount of gas and air introduced is such that substantially complete combustion of the fuel takes place while minimum excess oxygen over and above the amount necessary for complete combustion is introduced. The combustion flame is guided and directed toward but spaced from the articles being 3 peeled to produce a flow of the products of combustion through the heating zone. A controlled amount of moisture is introduced into the combustion products in the form of steam, water or superheated steam. Water is preferably introduced as a high pressure spray, i.e.-, as a mist or. fog, or water vapor such as steam may be injected. The water or other suitable liquid is flashed into superheated steam, or water vapor such as steam is superheated. In either event the superheated steam is mixed with the combustion products, and forms the heating medium or treating atmosphere for application to the articles being: peeled. The amount ofwater sprayed into the flame for production of superheated steam at atpears on the skin while the intermediate dotted portion of the figure illustrates the conditions in which the tomate peels easily and in which 110 char appears. It will be seen that the introduction of moisture considerably shortens the. time requiredfor skin conditioning. It will be noted also that the amount of moisture introduced can be varied widely and still obtain desirable results up to themaximum amount of water that can be introduced in a given atmosphere and, be maintained as superheated steam. The introduction of the moisture not only promotes efficient and rapid heat transfer from, the atmosphere to the articles being treated, but also serves to stabilize the heat conditions of the atmosphere and to enable uniform treatment of articles over along run.

The graph shown in Figure. 3 illustrates a theoretical curve of the percentage superheated steam in the treating medium at temperatures between 4500 degrees F. and 21-2 degrees using. natural gas as the fuel and for varying amounts of introduced water. The portion of the temperature range employed will. lie preferably between about 800 degrees to 900 degrees F. and 1200 degrees to 1500 degrees F., depending on the article being treated, the time of treatment, and other operating conditions. It will be understood that actual temperatures fall below those of the curve due to heat losses, and the drop in temperature will depend largely upon the insulatingefiiciency of a particular installation.

Referring to Figure 4,it will be noted that an increase in temperature reduces the time in the treating atmosphere', while also reducing the time in which char will occur. As a result the selection of operating conditions of the process requires a balancing of the various conditioris to obtain optimum results at a desirable cost figure. Dbviously, also, these conditions will vary with different products and with different types of varieties of the same product. With respect to vine ripened Pearson tomatoes, satisfactory results are obtained with a temperature of the treating medium of between 1000 degrees and 1100 degrees F. with the corresponding time ranges shown in Figure 4, i.e., between about eighteen seconds to about twelve seconds. At these temperatures, we have found that the outer skin can be removed without carrying with it an intermediate layer of meaty material which usually adheres to the skin and is removed therewith.

Also the volume of gas being burned and the air nec essary for complete combustion of the gas is controlled so that there is always a flow ofcombustion products past the articles being treated, thus they are completely entree gaseous mie'rtur'e' or he'a-ting medium containing super neared steam The flow of .the atmosphere pastthe 4 articles aids in the heat transfer operation. Preferably also the heating medium is controlled so that a portion thereof will flow out along the path of travel of the articles in entering and leaving the heating zone. As a result the articles may be subjected to and enveloped by this atmosphere for a selected amount of travel before entering and after leaving the actual heating zone. The exhaust gases may desirably effect a slight amount of preheating of the articles entering the zone and a slight amount of cooling of the articles in leaving the zone.

After the article has been subjected to the heating zone so that the skin is loosened and ready for removal, it is carried into a peel removing zone where the peeling can he carried out in a selected manner in accordance with the article being processed. With the processing of tomatoes, for example, the article may be hand peeled, or subjected to the action of suitable mechanical peeling means. With tomatoes and other articles the skin may be removed by a spray. In any event where desired, the material can be subjected to a spraying operation for cooling or for aid in skin removal after it leaves the heatingzone and before or during the operatioii ot'peu removal.

In carrying out the process in the peeling of onions, for example, the treatment is carried out at a temperature of about 1060 degrees F;; and a treating time at about forty-five seconds.

Referring to the drawings there is illustrated apparatus capable of carrying out the above described process and having certain novel details of construction as will be pointed out. Referring to Figures 1 arid 2, there is inns: trated a treating and peeling apparatus including a main frame 10 upon which a series of transverse agitating and peeling rolls 11 are carried by suitable chains 12tr'ained about suitable drive sprocket 13 at the discharge end of the machine and about idler sprockets 14 at the feed end thereof. The driving sprocket 13 is driven through" a suitable drive connection 16 from a conventional form of variable speed motor drive unit 17' having a control wheel 17a for controlling its speed. The rolls 11 be of any suitable construction such as metal.

At the feed end of the machine the rollers 11 travel through a preliminary feeding zone where washing sprays 23 of any desired construction may be provided for apply ing a spray of treating material to the articles being processed at a desired pressure after they are delivered to the rollers 11 from the feed chute 24. For example, these sprays may contain a wetting agent where a filni of moisture is desired on the products. After the rolls 11 leave the preliminary treatment zone they pass be heath a tunnel element 26 formed as an extension of a i the flue construction 27 provides for the passage of exhaustgases upwardly to the central stack 29. Within the semi-cylindrical combustion chamber 28 there are pro vided two transverse arrays of burners 31 leading to a common manifold 32 to which fuel in the forrnof gas is introduced through the pipe 33. Air for combustion. purposes is supplied through the pipe 34. The amount of gas admitted is controlled by means of a suitable valve under control of the manual lever 36 (Figure 1), while the amount of air is similarly controlled through a valve of conventional construction under control of the lever 37.

It is to be noted that the flame from the burners 31 is directed against the wall of the combustion chamber 28 and sweeps downwardly past an annular baflie 38 which is placed to separate the combustion zone adjacent burners 31 from aliquid introduction zone below bathe 38' in which a plurality of spray nozzles 39 of conventionalf construction are mounted. The nozzles- 39 receive supply of water under pressure from a manifold 40. The amount of Water to be introduced to the sprays is controlled through a suitable valve construction having a manual control lever 35 (Figure 1). It will be noted that the positioning of the spray nozzles 39 with reference to burners 31 is such that the water is introduced into the flame after its initial combustion zone so that there is no danger of quenching the flame by the introduction of water. At the same time the water is introduced and flashed into superheated steam before the combustion products and steam are applied to the articles being carried through the heating zone on the rolls 11.

It will be understood that the above structure may be modified for certain fruit and vegetable articles to place the combustion chambers in a more remote location with respect to the treating zone. Also the point of introduction of moisture can be varied to introduce the water into the combustion products in a location spaced from or remote from the zone of flame propagation.

To effect controlled application of the heating medium to the articles by effecting controlled shifting or rotation of the articles, the rolls 11 are provided with suitable sheaves or may be grooved to receive an overhead V-belt 41 which is trained about respective driving and idler pulleys 42 and 43. The pulley 42 is driven from a conventional variable speed drive unit (not shown) similar to the unit 17. The belt 41 extends from the feed end of the machine past the treating zone. By controlling the speed of the belt 41, the rate of shifting or rotation of the articles 44 may be controlled during treatment thereof.

As the rolls 11 with the artilces thereon leave the heating zone they pass beneath a second tunnel element 46 and enter the peel removal zone below sprays 45. If desired the sprays 45 above this zone may be used for removal of loose skin or peel. During this spray treatment the articles are moved or rotated by rotation of their supporting rolls under control of an overhead V-belt drive structure 47 having a variable drive unit 48.

After the rollers 11 pass over the discharge end of the machine and travel along the return stretch, they are subjected to sprays from the nozzles 49 to flush the rolls and remove the peel. The waste water and peel are discharged into the drain trough 50 of the machine.

It will be noted that with the control levers 36 and 37 properly adjusted as to the introduction of gas and air to provide the desired combustion characteristics, the water valve control lever 35 can be adjusted to vary the rate of water injection and thereby control the temperature of the treating atmosphere.

While we have shown and described a preferred embodiment of the invention, it will be apparent that the invention is capable of further variation and modification and its scope should be limited only by the scope of claims appended hereto.

We claim:

1. The method of loosening the skin of fruit and vegetable articles that comprises establishing a flame by supplying proportional amounts of fuel and oxygen for substantially complete combustion of the fuel within an otherwise oxygen-free combustion space, introducing moisture into the products of combustion for vaporization and superheating thereby before arrival of the products of combustion at a treating zone, and subjecting the articles to the vapor containing products of combustion in said treating zone to effect loosening of the skin thereof.

2. The method of skin conditioning of fruit and vegetable articles that comprises establishing a gaseous heating medium by burning a fuel to substantially complete combustion without excess oxygen, introducing moisture in controlled amounts into the combustion products for flash vaporization and superheating by the combustion products to provide a treating medium at atmospheric pressure, and passing the articles through the treating medium for treatment and loosening of the skins thereof.

3. The method of skin conditioning fruit and vegetable articles that comprises establishing a gaseous heating medium by burning a fuel to substantially complete combustion without excess oxygen, spraying moisture in controlled amounts into the combustion products for flash vaporization and superheating by the combustion products to provide a heating medium, passing the articles through the heating medium at a controlled speed for treatment and loosening of the skins thereof.

4. The method of peeling fruit and vegetable articles that comprises establishing a gaseous heating medium by burning a fuel to substantially complete combustion without excess oxygen, introducing moisture in controlled amount for substantially complete flash vaporization by the fuel flame and for superheating by the flame, passing the articles through the heating medium at a controlled speed for treatment and loosening the skins thereof, and effecting rotation of the articles while travelling through the heating medium.

5. The method of peeling fruit and vegetable articles that comprises establishing a gaseous heating medium by burning a fuel to substantially complete combustion without excess oxygen, introducing moisture in controlled amount for substantially complete flash vaporization by the fuel flame and for superheating by the flame, passing the articles through the heating medium, controlling the speed of travel of the articles to establish the time of treatment, eifectin'g rotation of the articles while travelling through the heating medium, and controlling the rate of rotation of the articles to establish uniform treating conditions of the surfaces thereof.

6. The method of skin conditioning of .fruit and vegetable articles that comprises burning a fuel to substantially complete combustion without excess oxygen to establish a gaseous treating medium, introducing moisture in controlled amounts into the combustion products to provide a treating medium at atmospheric pressure, and subjecting the articles to the treating medium for treatment and loosening of the skins thereof.

7. The method of peeling fruit and vegetable articles that comprises burning a fuel to substantially complete combustion without excess oxygen to establish a gaseous treating medium, introducing moisture in controlled amount for heating by the flame, passing the articles through the treating medium at a controlled speed for treatment and loosening the skins thereof, and eifecting rotation of the articles while travelling through the treating medium.

References Cited in the file of this patent UNITED STATES PATENTS 1,236,690 Dunkley Aug. 14, 1917 1,992,398 Ryder Feb. 26, 1935 2,218,466 Gray et al. Oct. 15, 1940 2,308,902 Weller Jan. 19, 1943 2,445,881 Hemmeter July 27, 1948 2,515,025 Vahl et al. July 11, 1950 2,631,628 Martin Mar. 17, 1953 

1. THE METHOD OF LOOSENING THE SKIN OF FRUIT AND VEGETABLE ARTICLES THAT COMPRISES ESTABLISHING A FLAME BY SUPPLYING PROPORTIONAL AMOUNTS OF FUEL AND OXYGEN FOR SUBSTANTIALLY COMPLETE COMBUSTION OF THE FUEL WITHIN AN OTHERWISE OXYGEN-FREE COMBUSTION SPACE, INTRODUCING MOISTURE INTO THE PRODUCTS OF COMBUSTION FOR VAPORIZATION AND SUPERHEATING THEREBY BEFORE ARRIVAL OF THE PRODUCTS OF COMBUSTION AT A TREATING ZONE, AND SUBJECTING THE ARTICLES TO THE VAPOR CONTAINING PRODUCTS OF COMBUSTION IN SAID TREATING ZONE TO EFFECT LOOSENING OF THE SKIN THEREOF. 